In the sequence of photolithography for manufacturing semiconductor devices, the following processes are sequentially performed to form a predetermined resist pattern on a target substrate, such as a semiconductor wafer (which will be referred to as “wafer” hereinafter). Specifically, a resist coating process is performed such that a coating liquid or resist liquid is applied onto the wafer to form a resist film. Then, a pre-baking process (PAB) is performed such that a heat process is performed on the wafer treated by the coating process. Then, a light exposure process is performed such that the resist film is subjected to light exposure in accordance with a predetermined pattern. Then, a post-exposure-baking process (PEB) is performed such that a chemical reaction is promoted in the resist film treated by the light exposure. Then, a developing process is performed such that the resist film treated by the light exposure is developed.
Conventionally, a resist pattern dimension (which will be referred to as “resist profile”), such as the line width (CD) or sidewall angle (SWA) of a resist pattern, to be formed by the photolithography sequence described above is controlled by setting focal correction in the light exposure process.
The sidewall angle (SWA) means the inclination angle θ1 of a line sidewall, as shown by the sectional view of FIG. 11 that shows a line of a resist pattern.
The resist profile is also affected by a heat process in the photolithography sequence, so the process conditions set for a heat processing unit need to be exactly controlled. In order to exactly control the temperature on the surface of a wafer in heating, the heating plate of the heat processing unit is segmented into a plurality of areas, which are respectively provided with independent heaters built therein, so that the temperatures of the heating areas can be respectively adjusted.
In this respect, if the heating areas of the heating plate are controlled by use of the same set temperature, the temperature on the surface of a wafer on the heating plate may become less uniform, due to the difference in thermal resistance between the heating areas, for example. Where the temperature on the surface of the wafer is less uniform, a resist profile, such as the line width (CD) of a resist pattern, becomes also less uniform.
In light of this problem, conventionally, the heating areas of the heating plate are respectively provided with temperature correction values (offset values) for fine adjustment of the temperature on the surface of a wafer. The set temperatures of the heating areas of the heating plate are prepared by correcting the heat process temperature with the respective temperature correction values (for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-143850).
As described above, conventionally, the uniformity in resist profile on the surface of a wafer processed by a photolithography sequence is controlled by temperature correction of the heating areas for a heat process, and formation of the resist profile is controlled by focal correction in the light exposure process.
However, with an advance in the miniaturization level of resist patterns in recent years, the focal correction in the light exposure process may be insufficient to fulfill control for forming a resist profile, such as the pattern line width (CD) or sidewall angle (SWA), with high precision.
Further, if the focal correction in the light exposure process is insufficient to fulfill high-precision control for forming a resist profile, the light exposure process is applied unevenly among areas of a wafer, so the resist profile on the surface of the wafer is less uniform.